From: Jason Gunthorpe <jgg@nvidia.com>
To: "Christian König" <christian.koenig@amd.com>
Cc: Leon Romanovsky <leon@kernel.org>,
kvm@vger.kernel.org, linux-rdma@vger.kernel.org,
Daniel Vetter <daniel.vetter@ffwll.ch>,
Oded Gabbay <ogabbay@kernel.org>,
Cornelia Huck <cohuck@redhat.com>,
dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org,
Alex Williamson <alex.williamson@redhat.com>,
Maor Gottlieb <maorg@nvidia.com>,
Sumit Semwal <sumit.semwal@linaro.org>,
linux-media@vger.kernel.org
Subject: Re: [PATCH v2 1/4] dma-buf: Add dma_buf_try_get()
Date: Tue, 6 Sep 2022 13:44:09 -0300 [thread overview]
Message-ID: <Yxd42anepRnmFJwe@nvidia.com> (raw)
In-Reply-To: <18b3dd75-7995-a2a8-372b-1fd5838dfe1d@amd.com>
On Thu, Sep 01, 2022 at 09:55:08AM +0200, Christian König wrote:
> Am 01.09.22 um 01:12 schrieb Jason Gunthorpe:
> > Used to increment the refcount of the dma buf's struct file, only if the
> > refcount is not zero. Useful to allow the struct file's lifetime to
> > control the lifetime of the dmabuf while still letting the driver to keep
> > track of created dmabufs.
> >
> > Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> > ---
> > include/linux/dma-buf.h | 13 +++++++++++++
> > 1 file changed, 13 insertions(+)
> >
> > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> > index 71731796c8c3a8..a35f1554f2fb36 100644
> > --- a/include/linux/dma-buf.h
> > +++ b/include/linux/dma-buf.h
> > @@ -618,6 +618,19 @@ int dma_buf_fd(struct dma_buf *dmabuf, int flags);
> > struct dma_buf *dma_buf_get(int fd);
> > void dma_buf_put(struct dma_buf *dmabuf);
> > +/**
> > + * dma_buf_try_get - try to get a reference on a dmabuf
> > + * @dmabuf - the dmabuf to get
> > + *
> > + * Returns true if a reference was successfully obtained. The caller must
> > + * interlock with the dmabuf's release function in some way, such as RCU, to
> > + * ensure that this is not called on freed memory.
>
> I still have a bad feeling about this, but I also see that we can only
> choose between evils here.
>
> Could you just call get_file_rcu() from the exporter with a comment
> explaining why this works instead?
I guess, are you sure? It seems very hacky.
Jason
next prev parent reply other threads:[~2022-09-06 16:44 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-31 23:12 [PATCH v2 0/4] Allow MMIO regions to be exported through dma-buf Jason Gunthorpe
2022-08-31 23:12 ` [PATCH v2 1/4] dma-buf: Add dma_buf_try_get() Jason Gunthorpe
2022-09-01 7:55 ` Christian König
2022-09-06 16:44 ` Jason Gunthorpe [this message]
2022-09-06 17:52 ` Christian König
2022-08-31 23:12 ` [PATCH v2 2/4] vfio: Add vfio_device_get() Jason Gunthorpe
2022-08-31 23:12 ` [PATCH v2 3/4] vfio_pci: Do not open code pci_try_reset_function() Jason Gunthorpe
2022-08-31 23:12 ` [PATCH v2 4/4] vfio/pci: Allow MMIO regions to be exported through dma-buf Jason Gunthorpe
[not found] ` <YxcYGzPv022G2vLm@infradead.org>
2022-09-06 10:38 ` Christian König
2022-09-06 11:48 ` Jason Gunthorpe
2022-09-06 12:34 ` Oded Gabbay
2022-09-06 17:59 ` Jason Gunthorpe
2022-09-06 19:44 ` Oded Gabbay
[not found] ` <YxiJJYtWgh1l0wxg@infradead.org>
2022-09-07 12:33 ` Jason Gunthorpe
[not found] ` <Yxiq5sjf/qA7xS8A@infradead.org>
2022-09-07 14:46 ` Oded Gabbay
2022-09-07 15:23 ` Jason Gunthorpe
[not found] ` <Yxi5h09JAzIo4Kh8@infradead.org>
2022-09-07 16:12 ` Jason Gunthorpe
[not found] ` <Yxs+k6psNfBLDqdv@infradead.org>
2022-09-09 14:09 ` Jason Gunthorpe
2022-09-07 16:31 ` Robin Murphy
2022-09-07 16:47 ` Jason Gunthorpe
2022-09-07 17:03 ` Dan Williams
2022-09-07 15:01 ` Robin Murphy
[not found] ` <YxiIkh/yeWQkZ54x@infradead.org>
2022-09-07 15:08 ` Christian König
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